Electroplating nickel



Patented Mar. 11, 1941 ELEOTROPIATING NICKEL Richard 0. Hull,

and Raymond A.

Lakewood, Hofl'man, Euclid, Ohio, anignora to E. I. do Pont de Nemours a Company, Wilmington,

Dcl., a corporation oi. Delaware No Drawing. Application March 1, 1941,

- Serial No. 381,402

1 Claim. (01. 204-49) This invention relates to the electrodeposition of nickel and is more particularly directed to nickel plating compositions and processes wherein there is employed as an addition agent a sulfurized proteinaceous material.

It is customary to use an organic addition agent in baths for the. electrodeposition of nickel but the agents heretofore employed have not led to entirely satisfactory results. Using prior art addition agents there are obtained nickel deposits which upon casual examination apear bright, but th surface of such deposits is actually uneven and rough. The deposits build up brightness quite slowly and a considerable period of plating time is necessary to obtain even a superficial appearance of brightness. A still greater difliculty arises from the fact that any roughness or imperfection in the base surface will show up in the finished nickel coating as dull and unattractive areas.

It is an object of the present invention to provide nickel plating compositions and processes of improved character. It is a further object of this invention to produce nickel deposits which are "smoother than those heretofore producible. It

is a still further object of this invention to provide.

nickel plating compositions and processes which will quickly produce nickel deposits of great brightness. It is a still further object to provide electroplating baths of increased covering power and which produce nickel deposits of a desirable character over a wider range of current densities. It is a still further object'of this invention to provide a levelling agent which may be added to a nickel plating bath to produce deposits of improved character. It is a still further object of this invention to provide nickel plating systems of high throwing power with respect to surface inequalities. Still further objects of the invention will become apaprent hereinafter.

The foregoing and other objects of this invention are attained 'by the'use of a sulfurized proteinaceous materialfor the modification of nickel plating baths. More specifically, it is preferred to use a sulfurized protein hydrolysate which preferably is produced by a carbon disulfide treatment of a protein hydrolysate. It is particularly desirable to employ such sulfurized proteinaceous materials in conjunction with addition agents which have a beneficial effect upon the brightness and other characteristics of nickel deposits.

The use of sulfurized proteinaceous materials for the modification of baths for the electrodeposition of metals broadly is set forth and described in an application of JohnH. Perry, Serial No. 381,403, filed concurrently with this application. The present application is directed to particularly meritorious compositions and processes in which the metal plated'is nickel.

The sulfurized proteinaceous materials are preferably used in nickel plating baths in such small amount that alon they have little or no effect upon the brightness of deposits. They introduce a new and much needed property to nickel coatings. Nickel deposits produced using the sulfurized proteinaceous materials according to the present invention possess a fluidity" of appearance and they have a surface with a lus-' trous beauty unlike the merely bright deposits heretofore produced. Baths containing sulfurized proteinaceous materials quickly build up bright deposits of nickel and the deposits-actually tend to cover and to make less noticeable any blemishes or imperfections in the base surface. While the levelling agent of the invention can be used to advantage in the production of dull nickel deposits which are subsequently to be buffed or in the production of any electrodeposit of nickel they will be found particularly useful in connection with bright nickel undercoats for chromium.

sulfurized proteinaceous materials are wellknown as compositions of mater and they are usually described in the art as pharmaceuticals. Examples of sulfurized proteinaceous materials are described in the Sadikoif German Patent 192,344 as well as in German Patent 238,843 and French Patent 395,402 as pointed out in the Huppert Patent 2,112,210. sulfurized proteinaceous materials are also illustrated in the Huppert Patent 2,112,210 which shows. sulfurized protein hydrolysate products which have been oxidized.

According to the preferred practices of this invention a sulfurized proteinaceous material is prepared by first hydrolyzing and then sulfurizlng a protein in very much the mannerdescribed in Huppert and the citations in Huppert. Any protein may suitably be used and good results may be obtained, for instance, with gelatin or glue or with an albumen such as blood or egg albumen.

A protein hydrolysate may be prepared by hydrolyzing the protein in any of the manners known to the art, for instance, by treating with a solution with an alkali such as calcium hydroxide. Hydrolysis may of course be effected by other known methods such as the use of pressure. While any method of hydrolysis of protein may be used, it is preferred to degrad the protein with an enzyme such as pancreatin or yD in.

Sulfurization of a protein hydrolysate to produce a sulfurized proteinaceous material can suitably be effected by the 'use of any sulfurizing agent such as ammonium polysulfide or sodium polysulfide but the best results have been obtained using carbon disulfide. The extent and character of hydrolysis and sulfurization should be so regulated as to obtain a sulfurized proteinaceous material which is rather readilybathsoluble. Particularly if ammonium polysulfide 3 or sodium pol: sulfide issused for the sulfurization some care .ust be taken to prevent oversulfurization a son will result in a partiallyinsolubl product.

The hydrolysis of a protein, as is well known, leads to the formation of alpha-amino acids to a greater or lesser extent depending upon the degree of hydrolysis. As a sulfurized proteinaceous material one may accordingly wish to use a comparatively pure product obtained by sulfurization of an amino acid. Economy, however, will ordinarily suggest that there be used a sulfurized protein hydrolysate such as sulfurized glue. Y

If desired, a sulfurized proteinaceous material may be made by the direct sulfurlzation of a protein. Products made by the sulfurization of a protein give good results according to the present invention and it is likely thatsome hydrolysis occurs simultaneously with the sulfurization. If desired, the sulfurization and hydrolysis may be conducted simultaneously by the use of suitable hydrolyzing agents and conditions together with sulfurizing agents.

The sulfurized proteinaceous materials of the Huppert Patent 2,112,210 are made employing a subsequent oxidation of the sulfurized protein hydrolysate and these oxidized products and other similarly modified materials may be used as addition agents for plating baths according to the present invention. It is to be observed that the products of the Huppert patent are not as readily soluble as materials which have not been oxidized and for this reason are not preferred.

The preferred sulfurized proteinaceous materials for use as levelling agents in nickel plating baths according to the present invention are those obtained by a carbon disulilde treatment of an enzyme-hydrolyzed protein. It is still more specifically preferred to use gelatin or glue as a starting point because of the excellence of the product obtained and the comparative cheapness of the starting materials. I

The levelling agents of this invention may advantageously be used in any nickel plating bath and excellent results have been obtained in standard sulfate-nickel plating systems which contain small amounts of chloride and boric acid in accordance with the usual commercial practices.-

Particularly excellent results have been obtained using the levelling agents in a nickel chloride bath which contains a small amount of sulfate radical, the ratio of chloride anion to sulfate anion being from about 5:1 to 20:1 on the basis of equivalents. Good results have also been obtained in similar chloride baths which contain a small amount of a plating system such as a tartrate or acetate which is amenable to addition agents, the ratio of chloride anion to the active anion of the added system being from about 5:1 to 20:1 on the basis of molecular equivalents. In this latter connection it is more specifically preferred to use a ratio of chloride anion to organic acid anion from about 5:1 to 20:1.

The sulfurized proteinaceous materials of thepresent invention may advantageously be used with addition agents or mixtures of addition agents known to the art for the modification of nickel chloride baths. They may, for instance, be used with addition agents such as the alkyl naphthalene sulfonic acids of Lutz-Westbrook Patent 1,818,229. Similarly they may be used with polysulfonates a shown in Schlotter Patent 1,972,693 or with the mono-sulfonic acids of Waite Patent 2,112,818. The alkyl aromatic sulfonic acid compounds of Flett 2,195,409 or the sulfuric acid reaction products of the Pine Patents 2,029,386

- similarly be included as in the last mentioned Harshaw and Long patent.

While as indicated the sulfurized proteinaceous materials ofthis invention may advantageously be used with any addition agent or material beneficial in nickel plating baths it has been found that particularly excellent results are obtained using the levelling agent with a sulfobenzalde- T hyde such as metaor ortho-sulfobenzaldehyde may be mentioned 2-phenyl ethylene sulfonic acid, 2-hydroxy-2-pheny1 ethane sulfonic acid, 2-phenyl ethane sulfonic acid, 2-pheny1 ethane- LI-disuIfonic acid, 3-phenyl propylene-2-sulfonic acid, 3-phenyl propionaldehyde-2-sulfonic acid, 3-phenyl propionic acid-Z-sulfonic acid, (l-methyl-l-sulfo) -3-ethylene-6-methoxybenzene, (1-

methyl-l-sulfo)-3-ethylene 5,6 methylenedioxybenzene, (l-methybl-suli'ol-3-ethylene-5,6- methylenedioxybenzene, 2-furyl ethylene sulfonic acid, 2-hydroxy-2-furyl ethylene sulfonic acid, 2- furyl ethane sulfonic acid, 2-fury1 ethane-1, l-disulfonic acid, 2-furyl propionaldehyde-l-sulfonic acid, 2-furyl propionaldehyde-l-methyl-l-sul-' fonic acid, ethylene-3-cyclopentyl-1-sulfonic acid, propionaldehyde-3-cyclopentyl-l-sulfonic acid, Z-naphthylethylene sulfonic acid, and 1,2-

diphenyl ethylene sulfonic acid. It will be observed that it is preferred that the cyclic substituent be selected from the group consisting of phenyl, furyl, cyclopentyl, and naphthyl radicals. Not only is it particularly advantageous to use these addition agents in combination with the levelling agents of the invention for nickel plating baths in general, but the combination has been found exceedingly efficacious in chloridenickel baths of the type described above.

If the sulfurized proteinaceous materials of this invention are used as the only addition agent for nickel plating, then it 'will usually be found desirable to use moderately large amounts. There may be used for instance from about 0.05 gram per liter to about 5 grams per liter.

Following the preferred practices of this invention using a second addition agent with the levelling agent" as heretofore described, the levelling action is obtained by the use of minute amounts of a sulfurlzed proteinaceous material. In most nickel, plating systems about 0.005 gram per liter will profoundly modify the character of the deposit and will greatly increase the throwing power of the bath. As small amount as 0.001 gram per liter has been found to have a markedly beneficial effect. Larger amounts up to about 0.5 gram per liter may advantageously be used with other addition agents.

The amount of a levelling agent to use in a asmaos nickel plating bath in any particular instance will depend upon whether or not a second brightening agent is used and upon the specific plating system employed. It will be simple in each instance to determine the precise amount to use with a few simple tests which can be carried out in a plating shop without special equipment other than the small test cells already in common use for this purpose.

In order that the invention may be better understood reference should be had to the following illustrative examples:

Example I A sulfurized proteinaceous material was first prepared. For this purpose one kilogram of glue was dissolved in five liters of water and to this solution was added one per cent of its weight of pancreatin. The solution was adjusted to a pH of 8.0 with ammonium hydroxide and was allowed to stand for about eight hours at a temperature of about 40? C. Fifty grams of finely powdered slaked lime and 100 cc. of carbon disulfide was then added ,to the still warm solution and the whole was agitated strongly for about two hours. The solution was then made slightly acid with dilute sulfuric acid and filtered to remove insoluble calcium sulfate. The product was then dried. A nickel plating bath was made up as follows:

Grams per liter Nickel sulfate (NiSO4-7H20) 350 Nickel chloride (NiClz-SHzO) 15 Boric acid (H3303) ..l 35 Sulfurized proteinaceous material 0.1

Temperature, 50 C.

A definite improvement in the smoothness of deposit was observed as a result of using sulfurized proteinaceous material according to this example.

Example I] The levelling agent caused the deposit to be exceedingly lustrou and bright. The bath was of improved throwing power and of improved hiding power by reason of the inclusion of the sulfurized amino acid product.

Example III A plating bath was made up using the agent as prepared in Example I, the bath having the following composition:

Grams per liter Nickel sulfate (NiSm'7HsO)- 23 Nickelchloride (NiClz-8HsO) 240 Boric acid (HsBOs) 60 Metasulfobenzaldehyde Sulfurized gelatin............ 0.005

Excellent deposits were obtained from this bath 6 covering power" by reason of the inclusion of the sulfurized gelatin.

In practice it was found that the bath of Example III could be used with cathode nickel asbe of excellent character.

Baths similar to those of Examples II and III were made up but using instead of the orthosulfobenzaldehyde the following addition agents in the indicated amounts:

Grams per liter Methylnaphthalene sulfonic acid 1.5 Isoproplylnaphthalene sulfonic acid 0.25

Naphthalene-2,5-disulfonic acid 2 Benzene sulfonic acid 5 Naphthalene sulfonic acid 1 Chloral hydr 3 Similar plating baths using addition agents as set out in the examples were also made up but using instead of the suliurlzed products prepared 'as inExample I suliurized products prepared as in the Huppert Patent 2,112,210 in Examples I, II, III, and IV and as generally described in the patent. Good results were obtained with agents of this character and good results were also obtained using products prepared according to specific procedures of Examples A and B of Sadikoff German Patent 192,344.

Plating compositions according to the present invention may be oliered to the trade as mixtures of a sulfurized proteinaceous material with another organic addition agent or with all or a part of the salts which serve as bath constituents. It will be understood that the term plating compositions" is used herein in the customary way to refer to a dry packaged mixture as oifered to the trade, to a concentrated solution suitable upon dilution for use as a plating bath, and to the plating baths themselves.

While we have shown certain illustrative com positions, baths, and processes, it will be understood that without departing from the spirit of our invention one skilled in the art may readily devise numerous compositions and processes employing a sulfurized proteinaceous material as a modifying agent for plating baths.

We claim:

An aqueous nickel plating bath of the nickel sulfate-nickel chloride type in which the chloride anion andsulfate anion are in the ratio of from 5:1 to 20:1 containing about from 0.001 to 5.0

and the deposits were "level" and had in mm ent "fluidity" by reason of the presence of the levelling agent. The bathhsd an improved thrcwingmersndsaimwcndhidingpomcr 16 grams per liter of a bath-soluble sulfurized gelatin.

- Number Name 4 Date 3,860 Gockei. Apr. 18, 1938 2.238.861 14nd et al. ADI. 15. 1041 OTHER REFERENCES aglletsl Finishing. Raub et al., June 1040, page 

